A police officer who spent seven years infiltrating underground protest groups
has said he had committed an act of “betrayal” and promised to "make
amends" to the campaigners with whom he worked.

Pc Mark Kennedy, 40, who went under the name Mark Stone, told environmental activists that he “hated” himself after posing as one of them. In his undercover guise, he is said to have been at the heart of an alleged plot by a handful of campaigners to break into and take over one of the country’s largest coal-fired power stations in a protest over climate change.

The officer was confronted by activists in October last year after they found his passport, disclosing his real name.

In a telephone conversation, a recording of which was obtained by the BBC’s Newsnight programme, he is heard suggesting he could give evidence for the defence and criticising the police tactics he was involved with as like using “a hammer to crack a nut”.

He is said to have told activists that the cost of maintaining his undercover persona was £250,000 a year. His change of heart prompted the collapse of the trial of six activists accused of conspiring to close the Ratcliffe-on-Soar power station near Nottingham.

The Crown Prosecution Service announced it was dropping the case at Nottingham Crown Court yesterday after the defence raised concerns about Pc Kennedy’s alleged involvement amid claims that he may have acted as an agent provocateur.

He has resigned from the Metropolitan Police and is believed to have gone abroad, concerned for his safety after being unmasked.

The months of surveillance are understood to have cost police £300,000. Court costs are estimated at £300,000 and the time spent by lawyers, police and court staff on the case is expected to bring the final bill to more than £1 million. The cost will be met by the taxpayer.

Scotland Yard have repeatedly refused to comment on the matter.

In the recording obtained by Newsnight, Pc Kennedy can be heard saying: “I really want to make amends I really do.

“I hate myself so much I betrayed so many people ... If I can help in any way then I’d like to.”

Speaking about the use of infiltrators he said: “I’m not the only one by a long shot, it’s like a hammer to crack a nut.”

Police are facing two investigations into their tactics after the collapse of the case. Nottinghamshire Police, who co-oordinated the action against protesters targeting Ratcliffe-on-Soar, have asked the Independent Police Complaints Commission to look into their conduct.

The force added: “Discussions are taking place with a number of bodies about commissioning a second review into the conduct of the undercover operation.”

Jenny Jones, a member of the Metropolitan Police Authority and a Green Party member of the London Assembly, said the use of undercover officers to police non-violent protesters was “a clear waste of money”. She said she would be asking Sir Paul Stephenson, the Metropolitan Police Commissioner, to publish guidelines for officers about “the difference between collecting information and acting as an agent provocateur”. In April 2009, protesters met to plan the largest action against climate change seen in the UK, which would allegedly have closed the power station at Ratcliffe-on-Soar for a week.

Organised by a handful of activists, with Pc Kennedy said to be a prime player and funder, they spread the word on the internet that action would be taken. They gave no details and asked anyone interested to meet at a school in Sneinton, Nottingham, to be briefed.

Shortly after that briefing, police arrived and arrested the 114 activists present.

Last month, 20 protesters were convicted of conspiracy to commit aggravated trespass after admitting they wanted to break into the E. on power station. They will now consider an appeal based on Pc Kennedy’s alleged involvement.

The defence of the six acquitted yesterday, who pleaded not guilty to the same charge, was that they were unaware of the details of the protest until they arrived at the meeting, and having heard the plans had decided not to join in.

Their lawyer, Mark Schwartz, said: “Serious questions must be asked relating to the whole policing of this protest.”